Strategy for the Use of Molecular Oxygen in Organic Synthesis

Taniguchi, Tsuyoshi

doi:10.1055/s-0040-1707240

Cited by 6 publications

(2 citation statements)

References 25 publications

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“…Ground state (triplet) O

is also used as an oxidant for many synthetic pathways (see, for example, Refs. [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ] and references therein) as it is a very abundant and environmentally friendly reagent. To circumvent the limitation imposed by the spin-forbidden characters of these reactions, most of them use metal centers as catalyzers.…”

Section: Introductionmentioning

confidence: 99%

Spin-Forbidden Addition of Molecular Oxygen to Stable Enol Intermediates—Decarboxylation of 2-Methyl-1-tetralone-2-carboxylic Acid

Ortega

Gil‐Guerrero

González-Sánchez

et al. 2023

IJMS

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The deprotonation of an organic substrate is a common preactivation step for the enzymatic cofactorless addition of O2 to this substrate, as it promotes charge-transfer between the two partners, inducing intersystem crossing between the triplet and singlet states involved in the process. Nevertheless, the spin-forbidden addition of O2 to uncharged ligands has also been observed in the laboratory, and the detailed mechanism of how the system circumvents the spin-forbiddenness of the reaction is still unknown. One of these examples is the cofactorless peroxidation of 2-methyl-3,4-dihydro-1-naphthol, which will be studied computationally using single and multi-reference electronic structure calculations. Our results show that the preferred mechanism is that in which O2 picks a proton from the substrate in the triplet state, and subsequently hops to the singlet state in which the product is stable. For this reaction, the formation of the radical pair is associated with a higher barrier than that associated with the intersystem crossing, even though the absence of the negative charge leads to relatively small values of the spin-orbit coupling.

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“…Ground state (triplet) O

Section: Introductionmentioning

confidence: 99%

Spin-Forbidden Addition of Molecular Oxygen to Stable Enol Intermediates—Decarboxylation of 2-Methyl-1-tetralone-2-carboxylic Acid

Ortega

Gil‐Guerrero

González-Sánchez

et al. 2023

IJMS

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“…Molecular oxygen is a key agent in a variety of photooxidation processes [1,2]. As a reagent, there are mainly three pathways to incorporate molecular oxygen into the product: (1) by the triplet 3 O 2 , which plays the role of a radical scavenger agent; (2) by the superoxide radical anion generated through a single electron transfer (SET) process; and (3) by the singlet 1 O 2 which is usually produced through the energy transfer between the excited photocatalyst and 3 O 2 [3,4].…”

Section: Introductionmentioning

confidence: 99%

Photooxidation of 2-(tert-Butyl)-3-Methyl-2,3,5,6,7,8-Hexahydroquinazolin-4(1H)-one, an Example of Singlet Oxygen ene Reaction

2020

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Singlet oxygen ene reactions produce 2-(tert-butyl)-4a-hydroperoxy-3-methyl-2,4a, 5,6,7,8-hexahydroquinazolin-4(3H)-one quantitatively during diffusion crystallization of 2-(tert-butyl)-3-methyl-2,3,5,6,7,8-hexahydroquinazolin-4(1H)-one in n-hexane/CH2Cl2 solvent mixture. To confirm this photo-oxidation, a 1H-NMR study in CDCl3 was performed with exposure to ambient conditions (light and oxygen), with neither additional reactants nor catalysts. A theoretical study at the B3LyP/6311++G** level using the QST2 method of locating transition states suggests a two-step mechanism where the intermediate, which unexpectedly did not come from the peroxide intermediate, has a low activation energy.

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Mechanistic Understanding on Iron‐Catalyzed CH Activation

Gallego

Baquero

2022

Handbook of CH-Functionalization

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Modern synthetic chemistry has explored the applicability of more abundant and less toxic transition metals based on their reactivity towards CH functionalization reactions despite their lower catalytic performance compared to noble‐metal catalysis. However, a strong understanding of the reaction mechanism is required to make a rational design of a catalytic system without the need to test a wide variety of conditions libraries with poor results. Mechanistic studies are not trivial, and comprehensive experimental and computational data is preferred to draw a complete mechanistic scenario for each catalytic system. In this sense, during the last decade, iron‐based catalysts have presented very prominent results in the CH functionalization arena. Nevertheless, there is plenty of room to improve their catalytic performance to reach activities to the noble metal‐based catalysts. Thus, in order to give an overview to the reader, we focus this review on the recent articles digging into mechanistic aspects from different perspectives covering spectroscopic analyses of possible reaction intermediates, kinetic, thermodynamic, and theoretical studies on iron‐based CH functionalizations following inner‐sphere mechanisms. Hence, the critical parameters and conditions are summarized to clarify the iron catalysts' mode of action on the CH activation to enhance their catalytic performances and look for more sustainable catalytic transformations with this metal.

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Strategy for the Use of Molecular Oxygen in Organic Synthesis

Cited by 6 publications

References 25 publications

Spin-Forbidden Addition of Molecular Oxygen to Stable Enol Intermediates—Decarboxylation of 2-Methyl-1-tetralone-2-carboxylic Acid

Spin-Forbidden Addition of Molecular Oxygen to Stable Enol Intermediates—Decarboxylation of 2-Methyl-1-tetralone-2-carboxylic Acid

Photooxidation of 2-(tert-Butyl)-3-Methyl-2,3,5,6,7,8-Hexahydroquinazolin-4(1H)-one, an Example of Singlet Oxygen ene Reaction

Mechanistic Understanding on Iron‐Catalyzed CH Activation

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